Amber Rose plans to seek a restraining order against Wiz Khalifah’s mom

Sources close to Amber tell TMZ … Amber’s furious that Katie Wimbush-Polk‘s hatred for her has spilled into the courtroom. Katie has sued Amber for defamation, claiming Amber’s allegation Katie’s an unfit grandmother is a big fat lie.

We’re told Amber believes it’s just a revenge lawsuit because Katie can’t let go of the fact Amber left her son 3 years ago, and Katie has tried to make Amber’s life a living hell ever since the split.

Katie’s also taken shots at Amber on social media, ripping her to shreds every chance she gets … like in 2015 when Katie jumped into the Kardashian-Amber beef and defended the Klan.

Amber wants a restraining order to keep her and Wiz’s 4-year-old son, Sebastian, far away from Katie … fearing that exposing Sebastian to Katie’s hatred for Amber will hurt the kid.